During the manufacture of integrated circuit devices (e.g., semiconductor devices), wafers are typically utilized which have photoresists formed thereon. During subsequent photolithography processes, the photoresists are usually exposed to light, and patterns are then typically formed. The top surfaces of the wafers may thereafter be selectively etched in accordance with the characteristics of the patterns. Ions may subsequently be implanted into the surfaces to form active regions in the wafers. As a result, circuits having predetermined electrical characteristics may be formed.
The ability of a photoresist to adhere to a wafer is typically important since it may directly impact the yield of an integrated circuit device containing the wafer. If a photoresist poorly adheres to the wafer surface, undercutting may occur in a subsequent etching process. Typically, this etching process is carried out isotopically, i.e., the etching is usually performed on upper and lower surfaces of a layer present in a device. A widened pattern may be formed as a result of the isotopic etching process. This pattern may become further widened in the event the photoresist detaches from the wafer surface. Such a detachment is often caused by poor adhesion between the photoresist and the wafer. The problem may be difficult to correct since a photoresist is typically hydrophobic and the surface of a wafer is typically hydrophilic.
A number of proposals have been set forth in attempting to address the above difficulties. One proposal focuses primarily on blasting filtered nitrogens which are often present on the surface of the wafer. Another proposal involves mechanically scrubbing a wafer surface.
Yet another proposal relates to cleaning the surface of a wafer by applying pressurized water thereto. For example, the water may be applied at pressures ranging from about 2000 psi to about 4000 psi. Thereafter, the wafer may be heat dried such that it's surface is potentially hydrophobic. Heat drying, however, may not be an effective technique for imparting hydrophobicity to a wafer surface. As a result, a photoresist may not adequately adhere to the surface. The above problem is potentially worsened with respect to semiconductor devices, since these devices are becoming more highly integrated with wafers contained therein having larger holes.
Accordingly, attempts to enhance adhesion have primarily centered on chemically treating a wafer surface. One proposal relates to painting the surface of a wafer with a xylene solution. Utilizing xylene, however, often results in poor drying efficiency. Another proposed technique relates to contacting the wafer with a dichlorosilane solution. Potential difficulties, however, may arise in connection with this solution. Specifically, the wafer may not display adequate adhesive strength. Additionally, since the dichlorosilane is hydrophilic, it is difficult to maintain it in a non-diluted state. Moreover, a sizeable number of small holes may be formed in a photoresist layer coated with dichlorosilane, which can hinder formation of a correct pattern therein.
In an attempt to confront the above problems, solutions containing hexamethyl disilazane (HMDS) have been applied to wafer surfaces. A typical HMDS solution is adhered to the wafer surface by a employing a vapor priming method. The vapor priming method is usually employed to enable the HMDS to potentially react with the wafer surface and thus form a hydrophobic organic layer on the surface. In particular, the hydrophobic organic layer is designed to be used as a medium for forming the photoresist layer. It is believed that conventional HMDS is formed on the surface of the wafer via a condensation reaction between the wafer and the HMDS as illustrated in the reaction formula (1) and FIG. 1. EQU 2(Si--O--H)+(CH.sub.3).sub.3 --Si--NH--Si(CH.sub.3).sub.3 .fwdarw.2(Si--O--Si(CH.sub.3).sub.3)+NH.sub.3 (I
As shown, ammonia gas is generated by the reaction. The presence of the ammonia may be potentially disadvantageous due to potential environmental risks. In particular, this problem may be exacerbated when a deep ultraviolet (DUV) wave source is employed during processing. A DUV usually has a wavelength which ranges between about 180 nm and 330 nm.
Notwithstanding these prior art attempts, it would be advantageous to provide a hydrophobic organic layer on a wafer surface which may provide adequate adhesion between the wafer surface and a photoresist layer thereon. Furthermore, it would be advantageous to provide such an organic layer with minimal environmental risks potentially associated therewith.